Phaedimus
Having thus concluded their mathematical foreknowledge of the mutations of the sun, of which Aristotle gives testimony, let me now relate their skill in arithmetic; but first of all, their knowledge in optics, of which Aeschylus seems not to have been altogether ignorant. For these are his words: Casting a squint-eye like the tunny. For tunnies seem to be dim-sighted of one eye. And therefore, when they enter the Euxine Sea, they coast along the land on the right side, and contrariwise when they come forth; prudently committing the care of their bodies to the best eye.
But wanting arithmetic in order to the preservation of mutual love and society one with another, they arrive in such a manner to the perfection of that science, that, in regard they are extremely desirous to enjoy the society of each other, they always make up their whole fry into the form of a cube, and make a solid of the whole number consisting of six equal planes; and then they swim in such order as to present an equal front in each direction. So then, if the observer of the tunnies does but exactly take the number of the side that he sees, he knows the whole number of the shoal; well knowing that the depth is equal to the breadth and length.
